Fetal fibronectin (FFN) levels have been used to predict labor onset in women. In vitro studies demonstrate that pro-inflammatory cytokines induce synthesis of FFN by amnion (JSGI 3 85, 1996). We wished to determine if experimental induction of amniotic fluid cytokines stimulates elevated FFN in the presence or absence of labor. Pregnant animals were instrumented with intraamniotic catheters, electromyographic electrodes and maternal and fetal vascular catheters. Uterine activity (UA; HCA=mmHg.sec/hr) was monitored continuously. Animals were divided into four groups 1) Group B streptococcus (GBS) inoculations (102-105 cfu, n=5) to choriodecidual space; 2) 10 fg interleukin-1 (IL-1 ) to amniotic cavity in the presence or absence of indomethacin (INDO, 50mg oral BID for 5 days, n=4); 3) oxytocin in increasing doses (4-32 mU/kg/hr) until contractions were induced and maintained for a minimum of 3 hr (n=8); and 4) no treatment with spontaneous delivery at term (n=2). FFN samples were obtained within 96 hr after stimulus or nocturnal UA pattern greater than 10,000 HCA (moderate UA, Group 4) by deep posterior fornix swabs and assayed by ELISA using Adeza Biomedical kits. Concentrations of FFN above human threshold level of 50 ng/ml (assay limit of detection) were considered elevated. Oxytocin-induced UA in preterm animals was not associated with elevated FFN. UA associated with subsequent delivery (spontaneous term or preterm induced by GBS or IL-1 ) had increased FFN. Neither GBS nor IL-1 increased FFN in animals not destined to deliver prematurely. This suggests that FFN is not detected in the vagina in the absence of other mechanisms leading to labor onset. ***** UA response n % elev. FFN Pre-Treatment* Post-Treatment and Range* GBS heavy 3 66 <50 326 (<50-845) GBS light 2 0 <50 <50 (<50) IL-1 + INDO light 5 20 <50 <50 (<50-89) IL-1 heavy 4 75 <50 272 (<50-337) Oxytocin heavy 8 25 <50 <50 (<50-1000) Term Labor heavy 2 100 <50 827 (645-1000) *median FFN (ng/ml)